Compressor unloader



F. P. LIVINGSTON COMPRESSOR UNLOADER Flled Aprll 8, 1927 Nov. 6, 1928INVENTOR FREMONT P LIVINGSTON BY ATTORNEY Patented Nov. '6, 1928.

4 UNITED STATES PATENT OFFICE.

FREMONT r. LIVINGSTON, or DENVER, COLORADO, ASSIGNOR TO THEwiis'rmenousn AIR BRAKE COMPANY, OF 'WILMEBDING', PENNSYLVANIA, ACORPORATION or PENNSYLVANIA.

Applieation filed April 8,

pressor at starting is subject to the pressurein the system andconsequently starts under v a considerable load, which causes thecompressor motor to consume a correspondingly heavy current and imposesa severe strain on the apparatus, while the speed of the motor isbuilding up to normal. s i 1 The principal object of my invention is toprovide an improved unloading device for. air compressors.

In the accompanying drawing, the single figure is a diagrammatic view ofa fluid compressing apparatus, showing my'improved unloadin meansembodied therein.

Accor ing to the drawing, the fluid compressing apparatus may comprisean electric governor device 1, having a switch memher 3 for controllingthe circuit of the compressor motor, an air compressor 4 havingassociated therewith an. unloading device 5 and a control valve device6.

The control valve device 6 comprises a casing, having a chamber 7containing a valve 8, subject to the pressure of a spring 9. The valve 8has a fluted stem extending through a wall of the casing and is adaptedto be engaged and operated by the movement of the governorswitch member3 to the position for opening the motor circuit.

The unloading valve device 5 comprises a casing containing a diaphragmhead 10, forming a chamber 11 at one side, containing a spring 12 actingon the diaphragm head and a chamber 13 at the opposite side connectedthrough passage 14 to the compressor discharge assage 15. Chamber 13 isalso connected y pipe 16 to the control valve chamber 7.

chamber 17 connected to the atmosphere I The unloading valve device alsohas a through a choked port 18 in a disc contained comranssoa UNLOAQDER.

1927. Serial mi; 182,092

in a screwplug having screw-threaded engagement with the casing wall andcontaining a poppet valve 19, adapted to seal on a seat ring 20 formedon an apertured plug 21 having "screw threaded engagement'in the casingand forminga wall between the chambers 13 and 17. The valve 19 iscarried by a stem, wh ch exten-dsthi'ough a centralopenmg in the plug 21and is secured to the dia phragm 10.- v i In operation, when thegovernor switch is in the position shown in th'edrawing, thecompressormotor circuitis closed and the compressor operates to compressair'into the discharge passage 15, thence past the usual discharge valve22' andthrough pipe 23 to a storage reservoir 2.

Whenthe pressure in the'reservoir 2 has been increased to apredetermined degree, the governor device 1 1S operated to cause theswitch member 3 to move up and open the the running of the compressor.

The switch member 3, upon upward movement to open the compressorcircuit-,engages compressor i'moto'r circuit and "thereby stop and opensthe control valve 8, which connects.

chamber 7 to the atmosphere. Chamber 7 being connected through pipe 16to the dia phragm chamber 13 and through passage 14 to the compressordischarge passage 15, the diaphragm chamber 13 and passage 15 are alsoconnected to the atmosphere.

Fluid under pressure in the reservoir 2 acts on the discharge valve 22to hold it seated, so as to prevent back flow into pas sage 15 and tothe atmosphere.

The venting of fluid under pressure from the diaphragm chamber 13permits, the pressure of spring 12 to shift the diaphragm head 10 andvalve 19 upwardly, so as to unseat the valve 19. V V 1 When the pressurein the-reservoir2 becomes reduced to a predetermined degree,

the governor device 1 operates to cause the switch member 3 to close themotor circuit I and start the compressor. The movement of the switchmember 3 to close the motor circuit also permits the valve 8 to close.

With the compressor discharge passage 15 connected to the atmospherethrough chamber 13, past the opened valve 19, through chamber 17 andthechoked port 18, fluid from the compressor flows to the atmosphere on thecompression stroke, consequently, at

starting there is substantially no resistance to the operation of thecompressor and it quickly attains normal speed.

The pressure of fluid in passage 15 and acting on the diaphragm 10 isgradually in creased, since the compressor supplies fluid under pressureat a greater rate than it can escape through the restricted port 18,until the pressure on the diaphragm is sufficient to overcome thepressure of the spring 12. The diaphragm 10 is then operated to closethe valve 19 and the compressor then operates in the usual manner torecharge the reservoir 2.

With the above described construction, the compressor will not bestarted under full load. but the load is gradually applied according tothe time required to obtain a suflicient pressure on the diaphragm head10 to close the valve 19. The rate of applying the load to thecrunpressor may be varied by changing the size of the choked port 18.

This unloading apparatus may be applied to an type of compressor. foreither fluid or liquid, and I do not desire to restrict my invention toany particular type of fluid compressor.

Having now described my iiivention, What I claim as new and desire tosecure by Letters Patent. is

1. In a pressure control apparatus, the combination with a fluidcompressor, of means for venting fluid from the fluid discharge side ofthe con'lpresso r and operated upon a predetermined increase in thepressure of fluid discharged for cutting oil the venting of fluid fromsaid discharge side.

2. In a pressure control apparatus, the combination with a fluidcompressor, of a movable abutment subject to the pressure of fluiddischarged from said compressor, and a valve operated by said abutmentfor opening a vent for fluid discharged from the compressor.

3. In a pressure control apparatus, the combination with a iluidcompressor, o'l a movable abutment subject to the pressure of fluiddischargedv from said con'ipressor. a valve operated by said abutmentfor venting iluid from the discharge side of the con'ipressor. andmeansoperated by a moving part of said governor for venting fluid fromsaid movable abutment.

l. In a pressure control apparatus. the combination with a fluidcompressor and a compressor governor, of a movable abutment subject tothe opposing pressures of a sprim: and the pressure of fluid dischargefrom said conuiressor, a valve operated by said abutment for ventingfluid discharged fron'i said compressor. and a valve ope 'ated by amoving part of said governor for venting 'fluid from said movableabutment.

In testimony whereof I have hereunto set my hand.

FREMONT P. LIVINGSTON.

